It is open enrollment season for health insurance and the federal exchange starts its second year in business on Saturday. The politics of healthcare are a year-round affair, and NPR's national political correspondent, Mara Liasson, joins us now to talk about the Affordable Care Act and what we can expect from Washington and from the new Congress in the next few months. Hi, Mara.

MARA LIASSON, BYLINE: Hi, Robert.

SIEGEL: Let's start with the federal exchange. What should we be looking for as people start signing up?

LIASSON: Well, we need to see if the website actually works and the administration is working hard to make sure that happens. Yesterday we heard the administration downgrade expectations for the number of people they expect to sign-up this season. The Congressional Budget Office had originally predicted 13 million. Yesterday, HHS said 9 million. Critics say a-ha, that's because the program isn't popular. But on the other hand, it could mean that the hundreds of thousands of people that some assumed would be dropped from their employer's plans and dumped onto the exchanges hasn't happened. The real number, though - the most important number is not the number people who sign up this year, but the number of people who are still uninsured at the end of this process.

SIEGEL: Now, Obamacare - The Affordable Care act was front-and-center in the Republicans' campaign. Tell us about the political pressure on the new Republican majority to get something done about it.

LIASSON: Well, they have to take a bite out of it. They can't repeal it lock-stock-and-barrel because they still have a president with a veto pen, but they will try to chip away. I think they have the votes to repeal the medical device tax. That brings in $28 billion over 10 years. I think they'll take aim at the employer mandate - redefine full-time workers to be 40-hour-a-week workers rather than 30. I think repealing the individual mandate - the requirement that every person have health insurance - will be much harder. That's a real linchpin of the law, and the president would surely veto that, and Republicans don't have the votes to override.

The big question is can the Republican Congress do something that would unravel Obamacare, or just take a few nicks out of it? Don't forget you've got millions of people who are getting these benefits now and the entire healthcare industry that does not want it dismantled.

SIEGEL: Now, the Republicans also made gains in the state houses. Does their sweep of governor's races mean that Medicaid expansion to be rolled back in some states?

LIASSON: That's a good question, but the bottom line is no big changes. Democrats had hoped if they had won more governor's races, it would have meant more Medicaid expansion. That won't be happening, but it doesn't mean there will be a big rollback because many Republican governors who opposed Medicaid expansion were reelected. And in those blue states like Massachusetts and Illinois and Maryland that have new Republican governors, those governors are not planning to reverse Medicaid expansion.

SIEGEL: Late last week, the Supreme Court agreed to take up a challenge the Affordable Care Act. What's happening there?

LIASSON: Well, they agreed to take up a case about language in the law that said subsidies should only go to people who buy insurance on a, quote, "state exchange." So the plaintiffs say that means no one should be getting subsidies if they buy insurance through the federal exchange. The drafters of the law say that's not what they meant, but this case is potentially a huge threat to the law.

SIEGEL: But the long and the short of it is we're going to be talking about Obamacare for another couple of years.

LIASSON: That's absolutely right. Now, it is possible after the president leaves office the law will be judged as - the Affordable Care Act - as an actual health policy and not as something that has embodied people's feelings about the president. But Republicans say they cannot repeal the law lock-stock-and-barrel without a Republican president. So the bottom line is Obamacare is not going anywhere for the next two years, but it will certainly continue to be a political issue maybe in the next presidential election.

SIEGEL: Do you think that we'll see the Republicans in both chambers put forward a substitute plan that they would prefer to have in place rather than Obamacare?

LIASSON: I don't see that happening. They have tried very hard over the last couple of years to coalesce around a replacement for Obamacare, and they haven't been able to do that.